@Barracudahockey: Thank you. May I ask if there's a particular O.S. 90-size engine you prefer? There are a number in the market ranging from .91 up to 1.05 that would fit my helicopter. Some are pumped; some not. My only experience with O.S. is with the airplane engines where I've not had the greatest luck. Not sure whether I've just gotten a couple duds or not, but I've never had problems with my Enya's or Super Tigre's.
Here's the list of heli engines I've been looking at. I'm kinda leaning toward the O.S. 105HZ-R DRS. I would really appreciate your (or anybody's) advice:

O.S. GT15HZ (gas)

O.S. 105HZ-R

O.S. 91HZ Ringed

O.S. 91HZ-R 3C Speed Red 61F

O.S. 91HZ-R 3D Speed Black 61G pumped

O.S. 105HZ-R DRS

YS 91SRS-Tareq w/ Fuel Injection

Are there other brands I should be looking at? This will be going into a SYNERGY N7